Current Wi-Fi systems have unaligned time division duplexed (TDD) transmissions where one access point's (AP) downlink transmission may interfere with another access point's uplink transmission. This inter-AP interference is particularly a problem in high density networks where wireless channels between APs are stronger than wireless channels between APs and terminals. If the APs are not aligned in terms of the downlink and uplink transmission intervals, then transmission by one or more APs will strongly interfere and possibly block reception at other listening APs. This causes poor area capacity (bps/km2), packet loss, and over all lower data rates.
FIG. 1 illustrates an example problem of unaligned transmissions from TDD Wi-Fi access points. FIG. 1 depicts a street canyon, where there is a direct Line of Sight (LOS) between the AP1 and AP2, and non-line-of-sight (NLOS) between the APs and terminals (user equipment UE1 and UE2). Thus, the coverage of AP2 is smaller than the interference range from AP1. If AP1 is transmitting a downlink signal DL at high power to UE1, AP2 will find it hard to hear a weak uplink signal UL from UE2.